DOVER — “I saw this happening from a mile away,” Catherine Fish said, reflecting on the death last week of a University of New Hampshire sophomore.

It was about 10 years ago that Fish first became concerned about the sexual tastes of her then-boyfriend, she said. Fish was a high school senior in Pennsylvania at the time, and she was in a long-distance relationship with a college student named Seth Mazzaglia.

It was January 2002, and Mazzaglia was attending Rensselaer Polytechnic Institute in Troy, N.Y., at the time, Fish said. She became acquainted with Mazzaglia through her best friend, another Pennsylvania native who was also attending RPI, and who had just ended a rocky relationship with Mazzaglia.

Fish said she knew she was taking a risk getting involved with Mazzaglia, but she had just ended her own relationship, and was eager to regain the comforts she had lost.

The pair began dating, and Fish traveled periodically to New York to see Mazzaglia. He also traveled south to Pennsylvania to see Fish, and accompanied her to her senior prom.

It was in a hotel room on prom night when things suddenly took a turn, Fish said. While engaged in a sexual act, Mazzaglia began to choke her.

“He put one finger on one side of my trachea, and his thumb on the other side, and then he started squeezing,” Fish said. “I said 'What the hell are you doing? Stop that.'”

She said Mazzaglia released his grip, but the incident gave her insight into what she believes to be one of her ex-boyfriend's sexual proclivities: a fetish for choking his partners.

Fish contacted Foster's Wednesday after learning of the murder of 19-year-old UNH student Elizabeth Marriott. The Massachusetts native disappeared on Tuesday, Oct. 9, and is now believed to be dead.

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Seth Mazzaglia Seth Mazzaglia, 29, of Dover, has been charged with murder in connection with the death of University of New Hampshire student Elizabeth Marriott.

Seth Mazzaglia, a 29-year-old Dover resident, has been charged with second-degree murder in connection with Marriott's death.

Although Marriott's body has not been recovered, prosecutors say they have gathered “credible” evidence indicating Mazzaglia suffocated or strangled Marriott inside his apartment on Mill Street on Tuesday, Oct. 9, the night she went missing.

Foster's Daily Democrat has learned the death occurred during a sexual encounter, although it's unknown whether Marriott was a willing participant.

The attorney general's office announced Marriott's death Saturday, and Mazzaglia was arraigned on the murder charge Monday.

Few details of the police investigation have been released, and documents relating to the case remain under seal at Dover District Court. Foster's has asked the court to release investigatory materials pertaining to the case.

In the absence of an explanation for the death, those who knew Marriott and her suspected killer have been puzzled by the crime.

Friends remember Mazzaglia, an aspiring actor and 2006 UNH theater graduate, as a “nice guy” who was enthusiastic about martial arts and active in local theater.

Mazzaglia also operated a number of online accounts, including a profile on the dating website OKCupid.com under the username “DarkKaiser.” Mazzaglia does not drink or take drugs, according to his page, which lists hobbies such as “gaming” and “watching movies.”

The same user name, DarkKaiser, was also used by a 29-year-old Dover, N.H., man on the website FetLife.com, an online meeting place for bondage and fetish enthusiasts. The profile indicates the user is interested in a “lifetime relationship, a play partner, princess by day, slut by night, a sub.”

Now 28, and living on the West Coast, Fish said she was stunned, but not surprised to learn of the charges against Mazzaglia this week.

After graduating from high school, Fish said she traveled to New Hampshire to live with Mazzaglia inside a basement unit at the Sawyer Mill Apartments, the spacious apartment complex in Dover where Marriott was allegedly murdered last week. The pair dated off-and-on for about 17 months, between January 2002 and May 2003, she said.

A phone directory from 2003 at the Dover Public Library indicates residents named “C Fish” and “S J Mazzaglia” both resided at the Sawyer Mill Apartments that year. The directory does not list the apartments they lived in, but does indicate the two residents shared the same phone number.

When Fish moved in, Mazzaglia had recently been kicked out of Rensselaer, and he was spending a lot of time with social groups at UNH, such as the school's “pagan circle,” she said. He was enthusiastic about the game Dungeons and Dragons, and was attending night classes at UNH in hopes of being accepted as a full-time student.

UNH had refused to accept Mazzaglia after he left Rensselaer, according to Fish, who said the refusal came as blow to Mazzaglia.

“You'll find with this guy that his ego must be appeased,” she said.

Fish said Mazzaglia never physically abused her during their relationship, but he was “severely sexually abusive” and “refused to accept 'No' as an answer.”

“He would throw a tantrum if I refused to have sex with him, to the point where like, throwing stuff,” she remembered. “It was very clear that 'No' wasn't an option, so it was coercion always in that regard.”

Fish said she believes Mazzaglia's interest in asphyxiation continued when they moved in together, but her recollection has grown hazy due to stress from the relationship.

However, there is one conversation Fish claims to remember clearly: Fish said Mazzaglia once told her to avoid wearing necklaces around him because “the urge to choke me was very strong.”

Fish said she was enrolled at McIntosh College, the former business college in Dover, at the time, and moved into the school's dorms when she finally decided to break off her relationship with Mazzaglia in May 2003. Fish said she didn't take action against him, such as filing for a restraining order, because she didn't perceive his actions as a form of abuse.

“I didn't think that what he was doing was wrong,” she said. “I knew I didn't like it, but because he didn't hit me, I didn't associate that with domestic violence.”

Since then, Fish said she has contacted UNH's Sexual Harassment and Rape Prevention service several times to discuss the situation, and has also relayed her experience with Mazzaglia at “Take Back the Night,” an annual event held on the UNH campus to raise awareness of domestic abuse and sexual assault.

A friend in New Hampshire contacted Fish to inform her about Mazzaglia's arrest, she said. Since then, Fish said she's been in contact with local police to relay the details of her relationship.

A spokeswoman from the attorney general's office and Dover Police Chief Anthony Colarusso both declined to comment on whether Fish has been in contact with investigators.

“I cannot comment one way or the other because it's an ongoing and active investigation,” Colarusso said.